System for discharging flue gases

ABSTRACT

Flue gases from a high-pressure blast furnace are led from above into a vertical duct terminating in a tubular nozzle with a downwardly converging section and an adjoining cylindrical (or prismatic) section respectively coacting with a tapering portion and a cylindrical (or prismatic) portion of an insert defining therewith a pressure-regulating gap of adjustable width and a substantially invariable throttling passage. A spray head in the duct above the insert irrigates the gases descending through the nozzle into a separating compartment in which they undergo a sharp change of direction whereby they are freed from accompanying solids wetted by the spray. The width of the regulating gap may be controlled by a pressure sensor actuating a solenoid to displace the insert.

United States Patent 1 Hausberg et al.

SYSTEM FOR DISCHARGING FLUE GASES Inventors: Gerhard Hausberg, Essen-Bredeney;

Karl-Rudolf Hegemann, Essen-Bergerhausen, both of Germany Gottfried Bischofi Ban Kompl. Gasr'einigungsund Wasserruckkuhlanlagen Kommanditgesellsehaft, Essen, Germany Filed: Mar. 16, 1972 Appl. No.: 235,208

[73] Assignee:

[30] Foreign Application Priority Data' Mar. 16, 1971 Germany 2112541 May 11, 1971 Germany 2123338 References Cited UNITED STATES PATENTS 3/1923 Jones 55/416 3/1940 Weir 261/D1G. 54

[ Oct. 29, 1974 3,140,163 7/1964 Hausberg 55/416 3,199,267 8/1965 Hausberg 55/210 3,626,672 12/1971 Burbidge 55/240 3,726,065 4/1973 Hausberg et al 55/226 FOREIGN PATENTS OR APPLICATIONS 870,812 6/1961 Great Britain 55/239 Primary Examiner-Bernard Nozick Attorney, Agent, or Firm-Karl F. Ross; Herbert Dubno ABSTRACT Flue gases from a high-pressure blast furnace are led from above into a vertical duct terminating in a tubular nozzle with a downwardly converging section and an adjoining cylindrical (or prismatic) section respectively coacting with a tapering portion and a cylindrical (or prismatic) portion of an insert defining therewith a pressure-regulating gap of adjustable width and a substantially invariable throttling passage. A spray head in the duct above the insert irrigates the gases descending through the nozzle into a separating compartment in which they undergo a sharp change of direction whereby they are freed from accompanying solids wetted by the spray. The width of the regulating gap may be controlled by a pressure sensor actuating a solenoid to displace the insert.

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- 1 SYSTEM FOR DISCHARGING FLUE GASES Our present invention relates to an apparatus for the removal of high-pressure waste gases from blast furnaces or the like preparatorily to utilizing them at reduced pressure in, say, a heat exchanger or a burner.

Flue gases from modern blast furnaces may exit at a pressure of about 3.5 atmospheres (absolute), so that a substantial pressure reduction is necessary to bring them down to atmospheric level.

In view of the high temperatures involved, conventional throttle valves are not suitable for this purpose. In'our copending application Ser. No. 188,557, filed Oct. 12, 1971 now US. Pat. No. 3,726,065, we have disclosed a system for scrubbing such waste gases in a wash tower equipped with pressure sensors upstream and downstream of an adjustable accelerator gap formed within the tower by a nozzle with tapering insert of the general type described in US. Pat. Nos. 3,140,163 and 3,199,267, the gases passing through this gap being wetted by one or more spray heads overlying the nozzle. The sensors control the gap width so as to maintain a substantial output pressure in the face of a varying input pressure.

The general object of our present invention is to provide an improved nozzle construction for the purpose set forth which positively maintains a substantially invariable minimal flow resistance so as to throttle the gas flow even under conditions of abnormally low input pressure (e.g. upon start-up of the plant); this dispenses with the need for a special control circuit of the type disclosed in our prior application which in the presence of such low pressure switches to an alternate mode of operation designed to maintain a constant pressure differential across the gap.

This object is realized, pursuant to our present invention, by providing the tapering insert within the tubular nozzle body with a downstream extension of a substantially constant cross-section, i.e., of cylindrical or prismatic shape, coacting with a geometrically similar section of the nozzle body to define therewith a restricted annular passage whose axial length preferably equals or exceeds that of the annular gap. Thus, a relative axial shifting of the insert and the surrounding nozzle body widens or narrows the adjustable gap around the tapering portion but has only a negligible effect on the flow resistance of the restricted passage defined by the extension of the insert.

If desired, several tapering insert portions of approximately the same axial length may be cascaded in as many converging nozzle sections to multiply the regulating effect of a single gap.

Advantageously, according to another feature of our invention, the restricted passage following the variable gap or gaps is provided with flow-retarding means such as, for example, an array of axially extending ribs integral with the nozzle and/or its insert to enhance the throttling action by introducing additional boundary layers; the flow-retarding means could also be in the form of discontinuities such as grids or perforated barrier disks in that passage designed to generate turbulence with resulting additional energy loss.

Whereas in the aforementioned prior systems the nozzle was generally mounted in a partition dividing the wash tower into an upstream and a downstream compartment, our present improvement may be embodied in a system lacking the upstream compartment so that the duct carrying the waste gases from the blast furnace or other source terminates in the nozzle body without widening into a shell around that body. This is so because there exists no longer a need for measuring the pressure differential across a partition in order to insure the maintenance of a predetermined minimum pressure drop. The downstream compartment, on the other hand, may serve the same function as in these earlier systems by causing the gas flow to be sharply deflected so as to separate it from substantially all accompanying solid particles wetted by droplets of water from one or more spray heads upstream of the nozzle. Aside from thus scrubbing the gas, the water spray also has the task of cooling the flow passing through the nozzle.

The above and other features of our invention will be described in detail hereinafter with reference to the acv of a plant including a blast furnace equipped with a system for the depressurization of its flue gases in accordance with our invention;

FIG. 2 is an axial sectional view, drawn to a larger scale, of a flow-regulating nozzle forming part of the system of FIG. 1;

FIG. 3 is a cross-sectional view taken on the line 111 III of FIG. 2;

FIG. 4 is a view similar to FIG. 2, showing a modification;

FIG. 5 is a further view similar to FIG. 4, showing yet another modification;

FIG. 6 is a cross-sectional view taken on the line VI VI of FIG. 5; and

a FIG. 7 is a view similar to FIG. 6, illustrating a further detail.

The plant shown in FIG. 1 comprises a blast furnace 3 with a flue 2 from which a duct 1 carries highpressure waste gases to a depressurizing apparatus embodying our invention. The apparatus includes a nozzle body 5, formed integral with the lower end of duct 1, surrounding an insert 4 with all-around clearance. As best seen in FIG. 2, the upper part 4a of this insert has a wider upstream end and a narrower downstream end so as to have a downwardly tapering configuration geometrically similar to that of the surrounding nozzle section with which it defines a gap 6 of variable width. A cylindrical downward extension 7 of tapering insert portion 4a or a width corresponding to that of the downstream end of that portion, defines with a surrounding portion of the nozzle body an annular passage 10 of constant width downstream of gap 6. Insert 4 is mounted on a stem 18 which rises from the base of a 1 separating compartment 17 and can be raised or lowered, as indicated by an arrow 9, with the aid of actuating means in the form of a solenoid 19 within compartment 17. A pressure sensor 20 detects the outlet pressure of the gases issuing from the nozzle and energizes the solenoid in a sense tending to keep that outlet pressure substantially constant.

A spray head 12, overhanging the insert 4 within the duct 1, irrigates the descending gas stream and cools it; the resulting steam moves with the gas through the gap 6 and the passage 10, expanding at the nozzle outlet and precipitating onto the entrained solids. Compartment 17 has an exit port 21 above the level of that outlet so that the gas must abruptly change direction (as indicated by the arrows in FIG. 1) in order to escape, thereby shedding the wetted particles which are collected on the bottom of compartment 17 in a trough not shown.

The embodiment of FIGS. 2 and 3 includes flowretarding means in the form of axially extending ribs 11 alternately secured to the inner wall of the nozzle body and the cylindrical extension 7 of the insert 4, thereby subdividing the passage 1,0 into a multiplicity of relatively narrow channels 8.

As illustrated in FIG. 4, an insert 4' may be provided with more than one tapering portion including, in this case, a portion 4b interposed between portions 4a and 7. This subdivides the adjustable gap into two zones 6a, 6b whose width, owing to the identical vertex angle of the tapers, varies identically upon axial motion of the insert.

An intervening gap zone 6c, of reduced axial length compared with zones 6a and 6b, contracts when the latter zones expand and should be made wide enough to avoid any significant obstruction of the gas flow within the stroke range of insert 4'.

FIG. shows a set of guide vanes 13 mounted in the duct 1 near the top of insert 4, these vanes being helically pitched at a small angle to the vertical axis (e.g. up to about 10) to impart a swirling motion to the gas flow. The ribs 11 within passage 10 are here also inclined, at a similar pitch angle but in the opposite sense, to increase the energy losses of the gas by changing the direction of flow. As further illustrated in FIG. 5, the lower end of the nozzle body 5 forms an outwardly flared skirt 14 defining two parallel annular channels 22 with a pair of downwardly diverging sleeves 15 secured to the nozzle body by narrow webs 16 which may also be helically pitched as shown, preferably in the same sense as the vanes 13.

The flared nozzle structure just described has already been disclosed in our aforementioned application Ser. No. 188,557 and has been claimed per se in another application, Ser. No. 235,149, filed Mar. 16,, 1972 as a continuation-in-part thereof.

The ribs 11 in passage 10 could be supplemented or replaced by one or more annular barrier disks 22' provided with peripherally spaced perforations 23 as shown in FIG. 7. In the presence of several such disks axially spaced within the passage, the perforations 23 may be relatively offset to throttle the flow still further.

As will be readily apparent from the preceding disclosure, a relatively slight vertical shift of the insert 4 or 4 substantially changes the width of gap 6 (or 6a, 6b) but has only a negligible effect upon the length and therefore the flow resistance of passage 10. In view of the limited displaceability of the insert, its extension 7 as well as the surrounding nozzle portion could also be slightly conical or pyramidal (rather than exactly cylindrical or prismatic) without materially altering the described mode of operation.

We claim:

1. An apparatus for depressurizing high-pressure waste gases, comprising: v

a duct having an inlet connected to a source of waste gases to be depressurized, said duct terminating in a nozzle with a first section converging toward an outlet formed by an outwardly flared skirt and a elongated second section of substantially constant cross-section between said first section and said outlet;

an insert received with all-around clearance in said nozzle, said insert having a tapering portion with a wider upstream end and a narrower downstream end defining with said first section a regulating gap of a width depending upon the relative axial position of said insert and said nozzle, said insert further having an extension of substantially constant width axially adjoining said tapering portion at said narrower down-stream end and defining with said second section a restricted passage exerting upon said gases a throttling effect substantially independent of said axial position; and

control means coupled to said insert for varying said relative axial position.

2. An apparatus as defined in claim 1 wherein said control means comprises pressure-sensing means at saidoutlet and actuating means for said nozzle responsive to an output of said pressure-sensing means for displacing said insert in a sense tending to maintain a substantially constant gas pressure in said outlet.

3. An apparatus as defined in claim 1 wherein said passage has a minimum axial length substantially equaling that of said gap.

4. An apparatus as defined in claim 1 wherein said nozzle is provided with a third section ahead of said first section converging toward said outlet at substantially the same angle as said first section, said insert having another tapering portion defining with said third section another regulating gap of a width substantially equaling that of the first-mentioned gap.

5. An apparatus as defined in claim 1, further comprising flow-retarding means in said passage.

6. An apparatus as defined in claim 5 wherein said flow-retarding means comprises an apertured barrier.

7. An apparatus as defined in claim 5 wherein said flow-retarding means comprises an array of generally axially extending ribs.

8. An apparatus as defined in claim 7 wherein said ribs are helically pitched at a small angle to the axial direction.

9. An apparatus as defined in claim 8, further comprising guide vanes in said nozzle ahead of said gap, said guide vanes being inclined to the axial direction at a small angle opposite the pitch angle of said ribs.

10. An apparatus as defined in claim 1 wherein said nozzle is centered on a generally vertical axis, said outlet being located below said passage.

ll. An apparatus as defined in claim 10, further comprising a separating compartment below said nozzle provided with an exit for said gases above the level of said outlet whereby said gases are deflected upon issuing from said nozzle, and spray means in said duct above said nozzle for wetting said gases to facilitate the shedding of moisture-laden solids therefrom in said compartment.

12. An apparatus as defined in claim 11 wherein said nozzle is further provided with a plurality of downwardly diverging sleeves in said outlet defining annular channels with one another and with said skirt.

13. An apparatus as defined in claim 12, further comprising narrow webs in said channels inclined at a small pitch angle to the vertical. 

1. An apparatus for depressurizing high-pressure waste gases, comprising: a duct having an inlet connected to a source of waste gases to be depressurized, said duct terminating in a nozzle with a first section converging toward an outlet formed by an outwardly flared skirt and a elongated second section of substantially constant cross-section between said first section and said outlet; an insert received with all-around clearance in said nozzle, said insert having a tapering portion with a wider upstream end and a narrower downstream end defining with said first section a regulating gap of a width dePending upon the relative axial position of said insert and said nozzle, said insert further having an extension of substantially constant width axially adjoining said tapering portion at said narrower down-stream end and defining with said second section a restricted passage exerting upon said gases a throttling effect substantially independent of said axial position; and control means coupled to said insert for varying said relative axial position.
 2. An apparatus as defined in claim 1 wherein said control means comprises pressure-sensing means at said outlet and actuating means for said nozzle responsive to an output of said pressure-sensing means for displacing said insert in a sense tending to maintain a substantially constant gas pressure in said outlet.
 3. An apparatus as defined in claim 1 wherein said passage has a minimum axial length substantially equaling that of said gap.
 4. An apparatus as defined in claim 1 wherein said nozzle is provided with a third section ahead of said first section converging toward said outlet at substantially the same angle as said first section, said insert having another tapering portion defining with said third section another regulating gap of a width substantially equaling that of the first-mentioned gap.
 5. An apparatus as defined in claim 1, further comprising flow-retarding means in said passage.
 6. An apparatus as defined in claim 5 wherein said flow-retarding means comprises an apertured barrier.
 7. An apparatus as defined in claim 5 wherein said flow-retarding means comprises an array of generally axially extending ribs.
 8. An apparatus as defined in claim 7 wherein said ribs are helically pitched at a small angle to the axial direction.
 9. An apparatus as defined in claim 8, further comprising guide vanes in said nozzle ahead of said gap, said guide vanes being inclined to the axial direction at a small angle opposite the pitch angle of said ribs.
 10. An apparatus as defined in claim 1 wherein said nozzle is centered on a generally vertical axis, said outlet being located below said passage.
 11. An apparatus as defined in claim 10, further comprising a separating compartment below said nozzle provided with an exit for said gases above the level of said outlet whereby said gases are deflected upon issuing from said nozzle, and spray means in said duct above said nozzle for wetting said gases to facilitate the shedding of moisture-laden solids therefrom in said compartment.
 12. An apparatus as defined in claim 11 wherein said nozzle is further provided with a plurality of downwardly diverging sleeves in said outlet defining annular channels with one another and with said skirt.
 13. An apparatus as defined in claim 12, further comprising narrow webs in said channels inclined at a small pitch angle to the vertical. 